Field of the Disclosure
The present disclosure relates generally to digital vector processing, and more specifically, to fractional delay estimation for digital vector processing.
Description of the Related Art
Digital signal processing components often introduce delays in the signals being processed as they traverse the forward processing path. In many instances, these delays can result in spurious or erroneous operation due to the resulting signal misalignment. To illustrate, many mixed signal systems employ digital pre-distortion to compensate for the non-linearity of a power amplifier or other non-linear front end device. However, the pre-distortion process typically relies on accurate signal alignment between the input signal and the pre-distortion signal, and thus such systems seek to characterize the time delay for the purposes of compensating for the time delay. Conventionally, the delay is estimated by computing the integer component of the delay using a windowing method, which provides a coarse resolution estimate of the location of a peak in the signal. The fractional component of the delay is then computed using a Farrow structure and fractional interpolation to search through the interpolated points for a finer-resolution estimate of the signal peak location. However, this conventional approach is computationally intensive in terms of time complexity. The precision of the fractional spacing is defined by the degree and number of taps in the Farrow structure, and the window used in the windowing method defines the maximum amount of delay that can be tracked for a given vector length. However, increasing window size for longer delays, or increasing the number and degree of taps in the Farrow structure, increases the computation time, and consequently power, which often is impracticable due to processing resource and power limitations.